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Answers for “为什么标准化输出包含负值?”

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Understand why

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Standardization centers data at the mean (μ\mu), so values below the mean become negative. Min-max normalization shifts and scales data so the minimum becomes 0 and the maximum becomes 1, keeping all values non-negative within [0, 1].

Conditions: Standardization uses z=x−μσz = \frac{x - \mu}{\sigma}.; Min-max uses Xnorm=X−Xmin⁡Xmax⁡−Xmin⁡X_{\text{norm}} = \frac{X - X_{\min}}{X_{\max} - X_{\min}}.

Meet the concept

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Standardization transforms a feature value xx into z=x−μσz = \frac{x - \mu}{\sigma}, targeting a mean of 0 and a standard deviation of 1 for the transformed feature.

Conditions: Applied per numerical feature.; Uses the feature mean μ\mu and standard deviation σ\sigma.; Assumes σ>0\sigma > 0.

Find a method

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Import `StandardScaler` from `sklearn.preprocessing`, instantiate it, and call `fit_transform` on the selected DataFrame columns. This transforms the data to have mean 0 and standard deviation 1.

Conditions: Input data is numerical.; Scikit-learn library is installed.